Huazheng HZJY880 Operating instructions

HZJY880

Computer BOD5 Measator

Huazheng Electric Manufacturing (Baoding) Co., Ltd

Contents

I. Introduction to the instrument and its scope of use ...................................................1

II. Working principle ....................................................................................................... 1

III. Main technical indicators ..........................................................................................2

IV. Installation and use .................................................................................................. 3

V. Analysis method and analysis steps ......................................................................... 4

VI. Normal maintenance and troubleshooting of common faults ............................... 16

VII. Precautions ........................................................................................................... 19

VIII. BOD5 Tester Packing List ....................................................................................21

I. Introduction to the instrument and its scope of use

Biochemical oxygen demand (BOD5) is a must-measured item for water quality evaluation

and an important quality indicator for measuring the pollution of water by organic matter.

880 type microcomputer BOD5 measuring instrument is a new type of instrument for BOD

measurement by air pressure difference method, which is processed by microcomputer and

liquid crystal display. It can accurately provide measurement results comparable to chemical

dilution method, directly display BOD value, and the biochemical reaction curve is clear at a

glance. The most ideal instrument for internal BOD determination. It can be widely used in

environmental monitoring, petrochemical, medical and health, teaching and scientific research

and other departments to monitor water quality.

II. Working principle

1、B0D5Fundamental

Biochemical oxygen demand refers to the amount of dissolved oxygen consumed or

required to decompose organic substances in water through the reproduction and respiration of

aerobic microorganisms in water under specific conditions.The BOD5value in water is usually

expressed by the amount of dissolved oxygen (mg/L) consumed by the sample placed at 20°C

for 5 days, and recorded as“BOD5”。

2、Determination principle

The stirrer is placed in the incubator, and according to the pre-selected range and

measurement range, a quantitative volume of water sample is poured into the culture flask, and

placed on the stirrer for continuous stirring. The temperature in the incubator was controlled at

Definition

Biochemical Oxygen Demand(BOD5)is defined as the consumption

of dissolved oxygen by aerobic microorganisms in water. The amount of

oxygen when the sample is placed in the incubator and the incubation

temperature is 20°C

After five days of culture, the dissolved oxygen consumed was measured

to determine the BOD value

20°C ± 1°C, and the water samples were incubated for five days after being kept at a constant

temperature. Sufficient dissolved oxygen must be ensured in the culture flask. The organic

matter in the sample undergoes biological oxidation, which is converted into oxides of nitrogen,

carbon and sulfur, during which the only gaseous carbon dioxide that escapes from the water

sample is absorbed by sodium hydroxide (or potassium hydroxide). Therefore, the reduction of

air pressure in the bottle is equivalent to the amount of dissolved oxygen consumed by

microorganisms. In this way, the BOD5value of the sample is proportional to the degree of air

pressure reduction in the bottle. The BOD5value can be obtained by measuring the change of

air pressure. Increasing or decreasing the amount of sample taken can increase or decrease

the pressure reduction value. This allows the operator to accurately measure a wide range of

BOD5values without complicated dilution steps. The change of air pressure in the culture flask

is detected by a semiconductor pressure sensor, and the BOD5value and biochemical reaction

curve of each sample are displayed cyclically by the LCD display.

III. Main technical indicators

1、Measuring range：0～1000 mg/L（when the BOD5value exceeds the measuring range,

it needs to be diluted）

2、Simultaneous determination of the number of samples: 6 samples or 8 samples each

time

3、Accuracy: in line with the national standard "GB7488-87"

（The BOD5value of the standard solution of glucose and glutamic acid is in the

range of 180 mg/L to 230 mg/L）

4、Display: The LCD display cyclically displays the BOD5value and biochemical reaction

curve of each sample.

5、Culture temperature：20℃±1℃

6、Power supply：AC 220V±22V 50Hz±0.5Hz

7、Power consumption：Instrument≤50Ｗ，Incubator≤300Ｗ

8、The instrument can save the BOD5values and biochemical reaction curves of the

eight samples analyzed last time

IV. Installation and use

（I）Environmental conditions for the installation of this instrument:：

1、Ambient temperature：0℃～40℃。

2、Relative humidity：≤80％

3、There is no strong vibration and strong electromagnetic field in the surrounding

environment.

4、The instrument should avoid direct exposure to strong light.

（II）Description of the functional components of the instrument

1、Front panel of the instrument host

Schematic diagram of the front panel of the instrument host

0-9：Numeric keys Yes/No: Operation prompt Yes/No key

Enter: Operation prompt and digital input confirmation key

Set time: press the "set time" button under the system time to modify the time;

2、The top of the instrument panel

Schematic diagram of the rear panel of the instrument host

1. Power switch 2. Power socket 3. Stirrer

During the experiment, it drives the stirrer in the culture bottle to stir the sample solution,

so as to promote the oxygen in the air in the culture bottle to dissolve in the sample

solution.

4、BOD culture bottle

The samples are put into culture flasks for biochemical culture. The culture flasks have

been specially screened and cannot be interchanged between each instrument, let alone

replaced by other similar flasks.

（III）Inspection steps of the instrument system

1、Check whether it is normal according to the instructions of the incubator. When the

control temperature is 20 °C, the accuracy after constant temperature should meet the

requirements of 20 °C ± 1 °C.

2、Place the host in the incubator, connect one end of the power cord to the host, and plug

the other end into the incubator.

3、Turn on the power of the instrument host.

4、Add a small amount of tap water to any culture bottle, put a stirrer as shown in Figure 3,

and place the bottles in sequence on the corresponding position of the upper cover of

the instrument stirrer. vortex. If all the above checks are normal, the experiment can be

carried out.

V. Analysis method and analysis steps

(I)preparation of four kinds of inorganic salts (nutrient solution);

Take four cleaned volumetric flasks with a capacity of 1 liter and prepare as follows:

1、Buffer

Dissolve the following reagents in distilled water and dilute to 1 liter.

（1）21.75g dipotassium hydrogen phosphate（K2HPO4）。

（2）8.5g potassium dihydrogen phosphate（KH2PO4）。

（3）33.4g disodium hydrogen phosphate （Na2HPO4·7 H2O humidity is stable at

61.07％～80.51％）。

（4）1.7g of ammonium chloride（N H4Cl）。

2、Magnesium sulfate solution

Dissolve 22.5 g of magnesium sulfate（MgSO 4·7H2O）in distilled water and dilute to 1

liter.

3、Calcium chloride solution

Dissolve 27.5 grams of calcium chloride（CaCl2）in distilled water and dilute to 1 liter.

4、Ferric chloride solution

Dissolve 0.25 g of ferric chloride（FeCl3·6H2O）in distilled water and dilute to 1 liter.

5、Nitrification inhibitor solution: Dissolve 500 ml of propylene thiourea in 1000 ml of

distilled water; generally, nitrification inhibitor does not need to be added to the water

sample. Add 1 ml of nitrification inhibitor solution per liter of dilution water.

（II）Measurement of actual sample BOD5

1、Turn on the power supply of the incubator, so that the displayed temperature of the

incubator is 20°C (see the instruction manual of the incubator for details). Put the host

into the incubator, connect the host and the incubator with the power cord, and turn on

the power of the instrument host.

2、Pre-estimate the range of the BOD5value of the sample to be tested, and select the

closest range. If it is impossible to estimate, the COD value of the sample can be

measured first, and then the BOD5value of the sample can be determined according to

the COD value of the sample (usually, the BOD5value of the sample is 0.8 times the

COD value of the sample). For samples with BOD5value below 1000mg/L and

containing enough aerobic microorganisms, no inoculation is required, and the

sampling amount can be directly obtained from the water sampling scale according to

the selected measurement range. According to the number of samples to be tested (up

to 6 samples can be measured, the instrument displays 8, and the latter two are not

used) to determine the use of several culture flasks to measure one of the samples. If

there are only two water samples, choose 2 to 4 culture bottles to measure one of the

water samples, estimate the range of the BOD5value of the water sample in advance,

determine the sampling amount of each culture bottle, and determine the required

amount of several culture bottles. total sample size. Place the water sample in a large

beaker (1000mL or 2000mL) and add 1mL of each of the four inorganic salts per liter of

water sample. Put the beaker into the incubator and stir on a stirrer at a constant

temperature (2-3 hours). At the same time, the pH value of the water sample must be

adjusted, which should be 6.7 to 7.5 (the optimum point is pH 7.2). If it exceeds this

range, it can be neutralized with an appropriate concentration of sodium hydroxide or

sulfuric acid. Then measure the water sample with the measuring cylinder according to

the determined sampling amount and pour it into the culture bottle. Similarly, other

water samples can be measured.

Table 1 Water sampling scale

Sample BOD5value range（mg/L）

Sampling volume

（mL）

0～25

485

0～50

433

0～100

358

0～200

265

0～300

211

0～400

175

0～600

130

0～800

104

0～1000

Note: If inoculation and dilution are required, samples should be taken according to the

above table after inoculation and dilution.

3、Put a stirrer in each culture bottle, and place the culture bottle on the corresponding

position of the agitator. Pay attention to the correspondence between the culture bottle

number and the channel number on the mixer panel. Generally, the shorter the

connection distance, the better, and specify the inside The bottle numbers are "2", "4",

"6", and numbers from the left, and they are located on the inside of the incubator; the

bottle numbers that are close to the plastic tube are "1", "3", "5", and numbers from the

left. , the position is outside the incubator; the order left of the 6 pressure sensors is "1",

"2", "3", "4", "5", "6", and the position is outside the incubator. Stir the test water sample

until the temperature of the water sample reaches 20°C ± 1°C (about 1 to 2 hours).

4、Take 6 cleaned sealed cups, put solid NaOH or KOH (or 5 to 6 NaOH particles) in the

cups that account for about 1/4 of the total height, and smear the two surfaces of the

sealed cups that are in contact with the bottle mouth and the connector Apply a thin

layer of vacuum silicone grease to the mouth of each bottle. If the sealing is good, it can

be left unpainted. Tighten the cap of the bottle connected to the hose on the culture

bottle, and at the same time plug the stoppers on the 6 reference air pressure chambers

on the stirrer. During this process, do not let NaOH or KOH fall into the culture bottle.

5、After 30 minutes of stability, operate the instrument host.

6、After the instrument host is turned on, the display is as follows:

7、The instrument will display the system settings after about 1 second

8、Press 1 and press Enter to modify the system time

Modification method:

Press the set time key, enter the system time to be modified, such as: July 23, 2005;

8:19:00. Enter 05-07-23-08-19-00 respectively, and press the Enter key to confirm, and

press the Enter key again to return to the system setting screen. If you do not need to

modify the system time, this step can be omitted.

Note: In July, you can't just enter a 7, you should enter 07, and the system will respond.

9、Press 2 and press Enter to query the experimental results. The following screen is

displayed:

This step is used to query the BOD5value and biochemical reaction curve of the last

six samples (channels 7 and 8 are random) stored in the instrument. Input the channel

number to be displayed and press Enter to confirm, the BOD value and biochemical

reaction curve of the channel will be displayed, press Enter again to return to the query

result screen, and press Enter again to return to the system setting screen. If the query

result is not required, this step can be omitted.

10、Press 3 and press Enter to automatically analyze. The following screen is displayed:

This sentence means that if the instrument fails to analyze continuously for some

short-term reason, if it has been analyzed for 30 hours, such as continuous analysis

Continue last interrupted analysis?

(Yes/No)

from 30 hours after restarting, select Yes, then only after another 90 hours of analysis

can be achieved. 120 hours of five-day analysis.

If you select No, the instrument will wait for about 10 seconds to display as follows: 1,

5 days of biochemical culture; 2, 10 days of biochemical culture; input 1, start 5 days of

biochemical culture; input 2, start 10 days of biochemical culture. At the same time, the

instrument enters the next screen.

Coefficient: Please select the channel number (1-8; the 7th and 8th channels are not

used), if you do not need to modify the coefficient of each channel, please press the

Enter key to enter the next screen. If you need to modify the coefficient, please enter

the channel number, enter the coefficient to be modified, and press the Enter key after

all channels have been modified. The so-called coefficient is the actual result of each

channel multiplied by the coefficient to get the displayed result.

When the modification is completed, press the Enter key to enter the next screen:

Enter the channel number to be modified (channels 7 and 8 are not used), such as 1,

after pressing the Enter key, the display is as follows:

Select the appropriate range, for example, press 4, then press the Enter key, the

instrument displays

After about two seconds of display, the instrument returns to the previous screen. The

default range of the instrument is 0-100mg/L. After each channel is set, please press the

Enter key to enter the next screen. The instrument starts from 0 hours, after 120 (or 240

hours of analysis. At this time, the instrument enters to display the BOD value and

biochemical reaction curve of each channel, and displays the current system time and

system running time at the same time, and the instrument displays the BOD of a channel

every minute. Values and biochemical reaction curves are printed every half hour.

After the analysis of the instrument is completed, the values of 8 channels are displayed in

a circular manner, waiting for the operator to shut down.

（III）Measurement data processing:

1、For undiluted samples, simply read the reading displayed on the instrument to get the

sample BOD value.

2、For the samples that have been diluted and inoculated, the readings on the display can

be read out, and then calculated according to the following formula:

Sample BOD5reading-Inoculum BOD5reading×Inoculum %

Sample actual BOD5＝

×Dilution factor

Sample liquid%

Example 1. There is a sewage sample whose BOD5 value is estimated to exceed

1000mg/L, so dilution pretreatment is done (no need to add inoculum). Select the range

from 0 to 600 mg/L, and the display reads 550 after five days of culture.

The actual BOD5value of the sample（mg/L）=550×2＝1100（mg/L）

Example 2. There is an industrial wastewater sample, the microorganisms are insufficient

to inoculate, and the BOD5value is about 60mg/L. The inoculation is carried out with

domestic sewage, and the inoculation amount is 10% (that is, 90 samples to 10 inoculum

solutions). The estimated BOD5value of the inoculum It is about 30mg/L, and the

industrial wastewater is in the range of 0-100mg/L during the experiment.

The inoculum of the parallel sample test was selected from the range of 0-50 mg/L

(sampling amount was specified in the respective range). After five days of incubation, the

display readings were 71.4 and 42.3, respectively.

Sample actual BOD5value（mg/L）＝

%90 %103.424.71 

＝74.6（mg/L）

Example 3. There is an industrial wastewater that is poisonous, and the estimated BOD5

value is about 700mg/L. Before the measurement, the sample was diluted 10 times and

inoculated with living water. The BOD5value of the inoculum was about 60mg/L, and the

inoculation amount was 10% ( 9 diluted samples, 1 inoculum), treated industrial

wastewater and inoculum were all sampled in the range of 0-100 mg/L. After five days of

culture, the numbers were 52.0 and 61.7, respectively.

Sample actual BOD5value（mg/L）＝

%90

%107.610.52 

×10＝509（mg/L）

（IV）BOD5test method for standard samples

In order to check the performance of the instrument, the standard sample of

glucose-glutamic acid can be used for BOD5test. Operators should be able to use the

instrument and chemical dilution operations correctly. The BOD5test method of

glucose-glutamic acid standard sample is as follows:

1、Prepare dilution water

Take a 2000mL beaker, measure 2000mL of distilled water with a measuring cylinder and

pour it into the beaker, and add 2mL of each of the four inorganic salts to the beaker,

which is the dilution water.

2、Dissolve 300mg of glucose（C6H1206）and 300mg of glutamic acid in 2 liters of dilution

water (such as laboratory glucose with a crystal water, glucose needs to be weighed

330mg, this standard solution should be freshly prepared before each use). Put a stirrer

in the beaker, and place the beaker on the amplifier in the incubator to stir at a constant

temperature for 2 to 3 hours.

3、Use a 1000mL beaker to take fresh domestic sewage as the inoculum, put the beaker

on the stirrer in the incubator and keep the standard sample constant for 2-3 hours at

the same time.

Figure 2 The water sample is poured into the culture bottle

Figure 3 The stirrer is put into the culture bottle

Figure 4 Figure 4 Put the CO2absorbent KOH or NaOH in the sealed cup

4、After the standard sample is completely dissolved, pour out 200mL from the graduated

cylinder, and then take 200mL of domestic sewage from the graduated cylinder and

pour it into the standard sample. The standard sample after inoculation is still placed on

the stirrer in the incubator and stirred at a constant temperature for 1 to 2 hours.

5、Measure the standard sample after inoculation according to the sampling amount

specified in the measurement range of 0-300mg/L in the table of instructions, pour it into

8 culture bottles respectively, and then perform the measurement according to steps

3-10 of the actual sample measurement mentioned above.

If the BOD5value is in the range of 180mg/L～230mg/L, it indicates that the method

used by the instrument is suitable and the result is correct. If the measurement result

deviates from the above range, it is necessary to check whether the performance and

operation of the instrument and the inoculation water meet the requirements (see

"Evaluation of measurement results").

（V）Factors Affecting BOD5

1、Determination

Dissolved oxygen

The samples taken in winter are supersaturated with dissolved oxygen because the

test temperature is set at 20 °C, and the samples taken in summer may be

under-saturated with dissolved oxygen at 20 °C. These samples should be stirred and

aerated prior to BOD5determination in order to adjust the dissolved oxygen to around

the 20°C saturation point.

2、pH

The pH value of the test water sample should be adjusted to 6.7 to 7.5 (the optimum

point is pH 7.2). The decrease in BOD5reading may be due to the pH value of the

sample being tested exceeds this range. For samples containing a large amount of

acid or alkali, the BOD5reading may be will be lower than the actual content.

Acidic or alkaline water samples should be neutralized with appropriate concentrations

of NaOH or H2S04.

If the industrial wastewater contains acid or salt oxides, or requires high dilution, for

the standard five-day BOD5determination, pH 7.2 phosphate buffer can be used as

the diluent.

3、Temperature

The stirrer was placed in an incubator at 20 °C ± 1 °C during the experiment. The

determination of BOD can also exceed this temperature range. For example, at 35°C or

37°C, the time required to measure BOD can be shortened to 2.5 days or 34 hours,

respectively, and the measurement results are similar to 20°C for five days. The BOD

value obtained by increasing the temperature has a good correlation with the results

measured at 20℃on the fifth day.

If the sample temperature exceeds 20°C when sampling, or the sample temperature is

less than 20°C, the sample can be kept in an incubator for constant temperature. The

sample is required to be processed prior to sample measurement.

4、Dilution

The measuring range of the instrument is 0～1000mg/L. If the estimated BOD5value of

the test sample is higher than 1000mg/L, the sample can be diluted with dilution water.

The added dilution water should also be kept at 20°C, and aeration should be used to

saturate the oxygen. If several identical samples are required to be tested, a sufficient

amount of the original water sample should be diluted, and the volume corresponding to

the measuring range should be taken from the diluted sample. . For example, when the

original water sample is diluted twice, the dilution factor is 2; when the original water

sample is diluted by 1:10, the dilution factor is 10.

5、Inoculate

Inoculation solution

The solution used for inoculation is the supernatant of untreated fresh

domestic sewage placed at 20°C for 24-36 hours.

In the next experiment, if you want to use the previously measured water

sample as the inoculum, it should be filtered through filter paper. This filtrate should

be stored under refrigeration (about 20 °C) and protected from light. Generally, it

may be effective within two months.

6、Inoculation method

Prepare inoculation solution

Put the sample to be assayed into a culture flask, and use a pipette to add 2 to 5 drops of

inoculum to the sample (depending on the sample size). Follow the steps to measure

BOD5, and the readings obtained after five days can be used as the true BOD5value of

the test sample.

NOTE: When inoculating using the above method. It is not necessary to correct

inoculated BOD5readings. Because the amount of inoculum added is too small relative to the

amount of water sample, it will not affect the BOD5reading. If the above methods fail to induce

biodegradation of organic matter in the water sample, the amount of inoculum added can be

increased. If the BOD5reading is affected by the addition of the inoculum, the inoculum and the

sample can be tested simultaneously for parallel sample determination. The amount of

inoculation is often 1%, 5%, and 10%.

VI. Normal maintenance and troubleshooting of common

faults

（I）The instrument should be placed in a ventilated place, without strong electromagnetic

field interference, without direct exposure to strong light, and without major power

fluctuations. It is best that the laboratory can be equipped with a regulated power

supply and has a good grounding wire.

（II）Open all the instrument packing boxes, put the host into the incubator, and connect

them with special cables.

（III）Cleaning work after the experiment

What is vaccination

The BOD5 test requires that the water sample contains organic

matter for biological oxidation and an appropriate amount of aerobic

bacteria that oxidize organic matter, as well as other microorganisms that

devour organic matter and promote the growth of aerobic bacteria. If there

is no or almost no such microorganisms in the water sample, a certain

proportion of such microorganisms must be added to the water sample. This

process should be called inoculation.

After completing the measurement, follow the steps below to clean

1、Culture bottle

Rinse the culture bottle with hot water several times, wash away the deposits on the

inner wall of the bottle with hot soapy water and a brush, and rinse with clean water

several times.

2、Stirrer

Wash the experimental stir bar with detergent solution and rinse.

3、Sealed cup

Wipe off applied vacuum silicone ester, wash off residue and CO2 absorber with wash

solution, rinse well and dry.

Note: The inner surface of the culture bottle stopper is often stained with sealing oil.

The inner surface must be wiped clean, and the vacuum silicone grease at the contact

between the connector and the sealing cup must be wiped off.

（IV）Troubleshooting of common faults

BOD5readings gradually increased during a five-day incubation period at 20°C ± 1°C.

(However, the increments between each day will be smaller and smaller over time).

The biochemical reaction curve (BOD5-time curve) will be similar to curve A shown in

the figure below. If similar curves cannot be obtained, the influencing factors can be

determined according to the following checklist.

Checklist

Result

Possible reason

Take measures

Reading drops

Air leak

Check whether the sealing cup

is in good condition, whether the cap

of the sealed culture bottle and the

sealing bolt are tightened, and

whether various impurities and

residues on the cap are removed.

Check the plastic pipes for cracks,

aging and deformation. When this

happens, a new tube should be

replaced, and attention should be

paid to the material length and inner

diameter of the original tube.

Result

Possible reason

Take measures

The instrument does not

respond

CO2absorbent

leaked, pH

changed, and air

leakage was

serious.

The range

selection is too

large, resulting

in interference

gas and so on.

Avoid putting too much absorbent

into the bottle as it will swell due to

absorbing CO2.

Find the leak point, mainly

check the pipeline connection.

Select the appropriate range.

This phenomenon may occur

due to many factors caused by the

sample. The influencing factors are

determined, and appropriate

pretreatment work is carried out

before the measurement.

Huazheng HZJY880 Operating instructions

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